If the internal structure of a body is changed by surgery, for example in a pelvic or brain operation, either by the surgery itself (e.g., advancing a guiding wire) or by after-effects (e.g., organs or tissue sagging), then it often can be useful if image data of the body are captured intra-operatively in order to detect the changes caused by the surgery. As used herein, the term “intra-operatively” refers to a period after a surgery and a period prior to further surgery.
Thus, for example, in a pelvic operation it is possible to check by one or more intra-operative scans the position at which a drill is situated in a bone. To this end, for example, a patient with a marker attached to him/her can be inserted into a computer tomograph. Computer tomography is performed on the patient and the patient is removed from the computer tomograph in order to perform further surgery. In such circumstances, it is advantageous if the patient is immobilized, e.g., the patient is situated in a fixed position relative to a table.
U.S. Pat. No. 6,678,545 B2 discloses a prior art system for use in imaging a subject and determining a position relative to a body of a patient. More particularly, this system can be used to determine a position of a probe within a head and display an image corresponding to the determined position. A drawback to this system, however, is that the probe and patient must be scanned together. The probe must be fully visible in the three-dimensional data set and, thus, can be an obstacle. Further, the probe may cause artifacts, which can deteriorate the image quality.